I 



ANTARCTIC BRYOZOA — ROGICK 275 



granular, with a row of large areolae separated from each other by- 

 short ridges at the periphery. Periphery depressed, with an occa- 

 sional salient mural rim. Central area of front moundlike, better 

 calcified and more elevated than the rest of the zooecium. Zooecial 

 boundaries distinct. 



Avicularia: Two small oval avicularia usually present and always 

 in the same position, one at each proximal corner of the orifice. An 

 occasional zooecium may lack one of these. The oral avicularia are 

 obliquely mounted on a small mound with their beaks pointing upward 

 and outward. A third avicularium is sometimes found on the frontal, 

 at the proximal end of the zoid (pi. 19,C), similar in appearance to the 

 oral ones and pointing toward the nearest orifice. Only two such 

 avicularia are in the fragment, both incomplete. Waters' specimens 

 apparently lacked them, since he does not mention them. Mandibles 

 of both types are similar, hemispherical and reinforced with a chitinous 

 rim. 



Orifice: The large variable primary orifice is often more angular 

 than rounded, appearing quadrangular to hexagonal in some zoids. 

 Distally it is rounded. Proximally it is straighter and more con- 

 tracted. A small thin bidentate process (?lyrula or umbo) slants 

 I inward from the center. Secondary orifice lepralioid. The three 

 bordering zooecial frontal walls aid in the formation of the short distal 

 and lateral peristome. The primary orifice is depressed below the 

 level of the rest of the frontal wall. The operculum is chitin-rimmed 

 ! around its upper hemispherical border but the boundaries of its thin 

 lower border could not be determined readily on our specimens. 



OviCELLs: Waters' specimens lacked ovicells. The current speci- 

 mens have young, salient, globose, hyperstomial ovicells whose frontal 

 wall has not yet been put in. So, the ovicell frontal remains un- 

 described until more material is found. 



Distribution and ecology: The present specimen grew on a heavy 

 mushroom-shaped species collected from Marguerite Bay, Station 

 180, in an 85-105-fathom dredge haul. Waters' specimens were on a 

 stone from a greater depth (500? meters) some distance south and 

 west (lat. 70°00' S., long. 80°48' W.) of the U. S. Navy specimens. 



Affinities: Waters felt that this species closely resembled Mucro- 

 nella bicuspis Hincks 1883, now Umbonula (Brown, 1952, p. 305). 

 Brown (p. 307) felt that Waters' Smittia dentata is not a Smittina but 

 might possibly be an Umbonula. 



A species very close to U. dentata but differing in the orientation 

 of the two avicularia and in the width and stoutness of the "lyrula" 

 is TJ. arctica (Sars) 1850, pictured by Osburn (1952, pi. 36, fig. 6) 

 and Robertson (1908, pi. 23, fig. 78). 



